Therapeutic solutions



Patented Sept. 10, 1946 2,401,412 mum-zone SOLUTIONS Douglas V. Frost, Waukegan, 111., assignor to Abbott Laboratories, North Chicago, Ill.,- a corporation of Illinois No Drawing. Application August 15, 1942,

Serial No. 454,919

10 Claims. (01. 167-81) 1 '2 The present invention relates to improved I therapeutic solutions and more particularly to 7 Per cent w/v stabilized riboflavin-nicotinamide solutions. The Riboflavin 0.10 preserl lt application is a congnuiiigniln-part of Nicotinamide 5.00 my p or application Serial 0. ,8

Riboflavin is a naturally occurring representac 32 ggg fi g figg gg g fifi tive of the polyhydyoxyisoauoxazine vitamins and s lu ti n i: comg lete. The solution is then cooled its deficiency 1s wldespread' Clinical symptoms and sufllcient acidic material, such as hydrochloof polyhydroxyisoalloxazine deficiency include no acid added to adjust the pH to about 45 keratitis, cheilosis, mydriasls, photophobia, etc. 10 to 66 Riboflavin is only very slightly soluble in water and hypodermical administration in this form 11 necessitates the use of large volumes of liquid. Per cent w/V The natural solubility of riboflavin in pure water Riboflavin 0.10 at 20' C., for example, is only about 0.013 per 15 Nicotinamidev 5.00 cent and the administration of a good therapeu- Thiamine hydrochloride 0.50 tic dose (10 mg.) at this temperature necessi- The above ingredients are mixed with about tates the injection of about 78 9 solution 80 per cent of the total volume of water required In my co'pending related apphcati? Serial in the formula and solution induced by warming. which t issued as Patent When solution is complete the resulting solution descnbed mephod for is allowed to cool and suflicient acidic material bilizing riboflavin by the formation of a ribosuch as monosodium dihydrogen phosphate flavin-boron complex. These boron compositions added to adjust the pH to about 4 to The proven highly F -Q as employ final solution is then made up by addition of .amounts of imectmn and chemically pure water. In certain cases, for exgg fi ig gigg figi gg g gggggf of ample. when preparing compositions containing p thiamm for oral administration the use of a pH During the research work carried out on th1s of 25 to 4 is preferred. investigation I also discovered that nicotinamide The present invention is not limited to the and water soluble saltsof nicotinlc acid solubilabove examples For example in place of the ized pol ydroxyis ll Such as riboflavinacidic materials described above other acidic buf- With continued investigation. including assay fers which are not objectional for parenteral intests running over relatively long periods of time jection, such as phosphoric acid, and the like I discovered that these compositions possessed may be used. In addition to thiamin, other vitathe desired physical stability but lacked the esmins, such as pyridoxine and salts of pantothenic sential chemical. or physiological stability. Exacid, may also be added as desired. The followtensive tests, for example, showed riboflavinin amp is il iv nicotinamide or -sodium nicotinate solutions to m be unsatisfactory for use after standing for sev- Per cent w/v eral weeks or months due to loss in vitamin po- Riboflavi 0,3 tency. Nicotinamide 10.0

The principal object of the present invention is Thiamin hydrochloride 1.0 to provide polyhydroxyisoalloxazine and partic- Pyridoxine hydrochloride 0.1 ularly riboflavin solutions of desired concentraa ci m pan 1.0 tions characterized by both physical and physio- Boric logical stability. The riboflavin, nicotinamide and acid ingre- Other objects will be appa n as h detailed dients of this example are preferably first mixed description hereinafter proceeds. 1 together in about 80 cc. of water and solution I have discovered that riboflavin-nicotinamide induced by warming. After solution the other solutions may be physiologically stabilized by adingredients are added and the resulting solution justing the pH value of the solutions to 2.6 to then made up t 1 by addition of distilled 6.6, and preferably from about 4 to 6.6. The fol- Water- In s example. which s a p of lowing examples will serve to illustrate the presabout the at o s 3% riboflavin t0 ent invention. nicotinamide. This represents a 50% increase in riboflavin over the riboflavin-nicotinamide ratio in Examples 1 and II. Increase in riboflavin was found possible by the discovery that the other vitamin ingredients used in this example are characterized by valuable additive riboflavin solubilizing effects. The solubilizing action of boric acid is also effective in Example III.

During the research investigation in this field, I discovered that nicotinamide possessed unique solubilizing effects when used in relatively high concentrations. I discovered, for example, that while 5 per cent nicotinamide solubilized 0.1 per cent riboflavin at pH 5.0, per cent nicotinamide solubilized 0.28 per cent riboflavin at pH 5 instead of 0.2 per cent as reported in early investigations. I also discovered that 20 per cent, 30 per cent, 40 per cent and 50 per cent nicotinamide at pH 5 solubilized about 0.6 per cent, 1 per cent, 1.6 per cent and 2.5 per cent riboflavin, respectively. These discoveries were unexpected for early investigations with relatively low concentrations of nicotinamide, i. e., up to 10 per cent as illustrated above, had indicated that doubling the percentage of nicotinamide merely doubled the percentage of dissolved riboflavin. However, the above figures (which are given as w/v) show that the amount of riboflavin solubilized is increased about 2.6, 6, l0, l6 and 25 times by using 2, e, 6, 8 and 10 times, respectively, the initial amount, i. e. 5 per cent, of nicotinamide. The following example will serve to further illustrate the present invention.

Per cent w/v Riboflavin 0.6 Nicotinamide 20.0

The above ingredients are dissolved with heating in water in the usual manner. When solution is complete about 0.2 per cent of a concentrated solution of hydrochloric acid is added to bring the pH of the final solution to about 5.0. If desired, about 0.5 per cent boric acid may be added as this ingredient in addition to its solubilizing efiects, has also been found to be an excellent physiologically inert bacteriostatic agent for use in the therapeutic solutions of the present invention.

After discovering the importanceof pH control in riboflavin-nicotinamide solutions with regard to the physiological stability of riboflavin, I made the further discovery that pH control in the acid pH range is essential to control of solubility or physical stability. For instance 5 per cent nicotinamide will solubilize about 0.1, per cent riboflavin at about pH 4.3 and above, but as the pH is lowered by addition of acid a progressive decrease in riboflavin solubility occurs. Thus at about pH 4.05, 3.6, 3.2, 3.0 and 2.5, 5 per cent nicotinamide will solubilize about 0.095 per cent, 0.07 per cent, 0.056 per cent, 0.044 per cent and 0.032 per cent riboflavin, respectively. Likewise, solutions of 10 per cent, 20 per cent and 30 per cent nicotinamide were found to have decreasing capacity to solubilize riboflavin as the pH was lowered below about DH 5. The decrease in solubilizing capacity of nicotinamide for riboflavin with decrease in pH is apparently related to salt formation between electropositive nicotinamide and electronegative acid anions. This appears likely because the pH curve of electrometric titration of nicotinamide follows the riboflavin solubility curve closely. For example, a 10 per cent solution of'nicotinamide hydrochloride, the

4 salt formed between molecular. equivalents of nicotinamide and hydrochloric acid, has 9. DH of 2.0 and has a low solubilizing capacity for riboflavin. Thus while the pH range which can be used to obtain physiological stability is 2.6- 6.6, the range which can be used to the greatest advantage from the standpoint of both physiological and physical stability (high solubility) falls roughly between pH 4 and pH 6.6.

The acidic solutions of the present invention contain the riboflavin in desired concentrations and of utmost importance retain their physiological potency over long periods of time. In

order to retain therapeutic potency in the present compositions the acidic material should be sumcient tolower the pH not only below the alkaline limit but also below the neutral point or pH l. Any acidic material which is substantially nontoxic at the concentration employed may be used.

Tests show that alkaline riboflavin nicotinamide solutions lose from about 33 to per cent of their riboflavin potency on standing for several months to a year at room temperatures. Tests also show that neutral solutions lose from about 15 to 30 per cent of their potency under similar conditions. While solutions of this latter type having a pH of 'l or slightly below come within. the range of usable compositions, experiments have demonstrated that such solutions must be used shortly after preparation or, if stored, must be kept at refrigerated temperatures in order to maintain the desired pharmaceutical stability.

The acidic solutions of the present invention make it unnecessary to use the solutions within a relatively short time after preparation and also make it unnecessary to keep the solutions under carefully controlled temperature conditions, i. e. below room temperature. In addition, as the acidic solutions are substantially free from physiological deterioration, the present invention makes it unnecessary in ordinary commercial practice to run frequent biological rechecks for such deterioration.

The riboflavin compositions solubilized by nicotinic acid salts are not stable under the 2.6-6.6 pH range employed in the above nicotinamide solutions. The solutions employing salts, such as the sodium, monoethanolamine, methyl glucamine, etc. nicotinates must be maintained at a pH of about 6 to 6.6.

It will be understood that the present invention is not limited to the above illustrative examples. All modifications of the present invention are in tended to be covered by the following claims.

I claim:

1. A therapeutic composition comprising an acidic aqueous solution containing at least about 1 mg. of riboflavin per cc. and at least about 50 mg. of nicotinamide per cc. and a small amount of acidic material suflicient to maintain said solution at a pH of 4 to 6.6.

2. A therapeutic solution comprising an acidic aqueous solution containing more than 0.2 per .the riboflavin present being not. less than 2% of the nicotinamide present.

6. A stable therapeutic preparation comprising an aqueous solution having a pH 01' 4-6.6 and containing riboflavin and a solubilizing agent consisting of nicotinamide, the nicotinamide being present in amounts between 30% and 50%; the riboflavin present being not less than 3.8% of the nicotinamide present.

'7. A therapeutic composition for parenteral use and stable for a time period of a, year or so comprising an aqueous solution containing riboflavin in excess of 0.013%; said solution containing also nicotinamide to solubilize the riboflavin; and sufllcient acidic material to adjust and maintain the pH of the solution at values between 2.6 and 6.6. a

.8. A therapeutic composition for parenteral use and stable for a time period of a year or so comprising an aqueous solution containing riboflavin in excess of 0.013%; said solution containing also nicotinamide to solubilize the riboflavin; and suflicient hydrochloric acid to adjust and maintain the pH of the solution at values between 2.6

and 6.6.

9. A therapeutic composition for parenteral use and stable for a time period of a year or so comprising an aqueous solution containing riboflavin in excess of 0.013%; said solution containing also nicotinamide to solubilize the riboflavin; and suflicient monosodium dihydrogemphosphate to adjust and maintain the pH of the solution at values between 2.6 and 6.6.

10. The process of stabilizing an aqueous riboflavin solution to prevent decomposition over a time period of a year or so, and to retain the riboflavin in solution for the same period, which comprises: adding nicotinamide to prevent precipitation; and preventing decomposition by the addition of suflicient acidic material to maintain the pH at about 4.5.

DOUGLAS V. FROST. 

